TVC LCD AMSTRAD 26” REPAIR CARD

Brand : Amstrad   26”

Model : T2712                                                                               Roberto Salerno

Schematic : not found                                     

Fault : A hint of brightness on switch on  then nothing. 


 When switched on at main I had an indication of brightness; then nothing but the standby  led  flashing  in continuation. Obviously there is no audio.  

These  Amstrad power supplies are well known to  easily  "give up"  after some  time. 

After removing  the  protection cover  I see that the power supply is a   AUO type, a typical instrument adapt for power supply  on  AUO Optronic  LCD panels. 

I  immediately notice  a swelling on the CAP  C355 (1000 F-25V-105°). 

I dislodge  the Power Supply from it's seat  removing the four screws and connectors attached to it.  I replace the CAP with a  higher operating  tension one,  precisely  105°C. 

On these power supplys  it is always advisable to check  the weldings on the various connectors,  I fresh solder any  suspicious ones...…

 I also  replace without delay any suspicious CAPS.  

I reassemble  all and give power to the unit,   after a few seconds of flashing  the  front led (preliminary  bootup phase ) switches on as usual. 

 If it is necessary to replace the power supply  on these Amstrad LCD  instruments  you must choose one with the correct  tension, in particular  those going to the panel. 

 So  if we have a AUO  panel  we must use a  AUO Power Supply  and  if we have a LG panel, we must use a LG power supply  etc...etc.... 

Visually, these power supplys are very similar  but it is dangerous to substitute them.  In particular , if a  LG type power supply  is inserted on a AUO  panel , we  seriously risk  damaging  the panel in a  irreparable way. After keeping it on trial basis I had the unit restored to full operation. 

 

Schaub Lorenz DVD Player REPAIR CARD

Brand: Schaub Lorenz

Model: SL 27900

Schematic: not found

Fault: no disc reading                                                                             Riccardo Omage

This DVD reader is a rather up-market brand, but nowadays with most electronic devices arriving from China, at a low cost, even if it is almost new, there it is on my work bench for repair.

On the initial display, humming bars appear, they disappear after a few seconds.

The Dvd disc loads regularly but the disc motor is running slow speed, at the same time the humming bars reappear also a loud humming noise. The disc stops and “no disc“ appears.

On all the secondary power supply voltages tensions in output, we find a ripple as can be seen in the photo, it can be found in more evidence on 5V and on 3,3V rather than on 12V.

This ripple has a main A.C. frequency, therefore I replace the CAP 33uF-400V (C1) on the primary side, note that it filters the tension in output from the Graetz bridge: I obtain a fully working unit.

Please note that the faulty CAP did not appear to be swollen or even leaky, so after having dismantled the unit no visual faults appeared.

It was the E.S.R. tester that revealed the faulty CAP (completely opened).

I was really surprised as it is not often that I find a CAP in this particular condition.

Considering the noise hum, even if it is irregular it seems to me to be an “old” fault found in a modern device; but browsing through other technicians repair cards and reading the pages of “Us Repairers”, I have come to the conclusion that CAPS sold nowadays are not what they used to be. Particularly the one found in this position, I have very rarely found it faulty, as for the others, well they started requiring replacement after five or six years of constant use…

This repair seen from the economic side of things may be seen as anti-economical, but at the same time it was not very time consuming and the spare part used was inexpensive, so I can be done. The opposite to what I thought before opening the unit.

When the fault signalled is “no disk”, immediately one would think of a faulty optic group, which is usually the cause of such faults.

Nothing can be taken for granted in this strange world of electronic repairs!!!

Roberto Salerno’s comment: here is another example of a faulty smoothing CAP which may be the cause of many problems, including lack of DVD disc reading.

I can confirm that CAPS are our main job source nowadays.

And thank God that they exist…